Family resemblances in handedness and hand posture while writing will be assessed by observing the writing behaviors of at least two family members (parents and/or offspring) in each of 1,000 families, by obtaining questionnaire data regarding the handedness and hand posture in writing of family members not assessed directly, and by obtaining other laterality data from those persons who will have been assessed directly. The design permits the assessment of the validity and reliability of questionnaire responses regarding handedness and hand posture. Resemblances in handedness and hand posture will be assessed, and the degree to which they fit various genetic models will be ascertained.